for hitachi ex-120.......head gasket was leaking(blowing air into radiator)..we found the problem,,,had the head milled down and ready to go....anyone know how much torque on head bolts, and what the valves are set to? thanks!
the 4BD1T and 6BD1T use the same specs. valves in and exh are .4mm cold. the head bolts use torque turn method. they suggest new bolts if they have been removed. however look to see if the thread appears to be ok at the end of the shank and the top threads try them again. if you see any stretch don't use it. grease the threads and under the bolt heads .1st round tighten to 50 ft lbs. 2nd round 65 ft lbs .the next round mark the bolt head than turn it 90 degrees or 1/4 turn. if the bolt feels like it is spongy or stretching remove and replace it
You better get ahold of the Isuzu dealer for the proper torque and procedure. They used to give away the service manuals for those engines. Do a search on the net for Isuzu service for a dealer. I know that Hamilton Engine in Portland, Oregon is the dealer in the northwest and they are real good about sending info. Good Luck!
thanks guys appreciate your time!